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            <h1>LinkedList 基于JDK11</h1>
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              Posted by zhuang on
              2020-04-14
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        <p><img src="image-20200414101327110.png" alt="image-20200414101327110"></p>
<h3 id="一、属性"><a href="#一、属性" class="headerlink" title="一、属性"></a>一、属性</h3><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">transient</span> <span class="keyword">int</span> size = <span class="number">0</span>;</span><br><span class="line"></span><br><span class="line"><span class="comment">/**</span></span><br><span class="line"><span class="comment"> * Pointer to first node.</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="keyword">transient</span> Node&lt;E&gt; first;</span><br><span class="line"></span><br><span class="line"><span class="comment">/**</span></span><br><span class="line"><span class="comment"> * Pointer to last node.</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="keyword">transient</span> Node&lt;E&gt; last;</span><br></pre></td></tr></table></figure>
<p>LinkedList的属性都被<code>transient</code>修饰，表示属性不参与序列化。</p>
<p>LinkedList是由若干个节点连接而成。</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">private</span> <span class="keyword">static</span> <span class="class"><span class="keyword">class</span> <span class="title">Node</span>&lt;<span class="title">E</span>&gt; </span>&#123;</span><br><span class="line">    E item;</span><br><span class="line">    Node&lt;E&gt; next;</span><br><span class="line">    Node&lt;E&gt; prev;</span><br><span class="line"></span><br><span class="line">    Node(Node&lt;E&gt; prev, E element, Node&lt;E&gt; next) &#123;</span><br><span class="line">        <span class="keyword">this</span>.item = element;</span><br><span class="line">        <span class="keyword">this</span>.next = next;</span><br><span class="line">        <span class="keyword">this</span>.prev = prev;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
<p>Node节点定义了前驱节点和后继节点，所以说LinkedList内部维护一个双向链表，item保存当前节点的值，next指向下一个节点，prev指向上一个节点</p>
<h3 id="二、构造函数"><a href="#二、构造函数" class="headerlink" title="二、构造函数"></a>二、构造函数</h3><p>LinkedList的构造函数有两种：1.无参构造函数；2.参数为集合</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br></pre></td><td class="code"><pre><span class="line"> <span class="comment">//默认创建一个LinkedList</span></span><br><span class="line">LinkedList&lt;String&gt; s1 = <span class="keyword">new</span> LinkedList&lt;&gt;();</span><br><span class="line"></span><br><span class="line"><span class="comment">//创建一个将其他类型集合中的数据转化为LinkedList</span></span><br><span class="line">LinkedList&lt;String&gt; s2 = <span class="keyword">new</span> LinkedList&lt;&gt;(<span class="keyword">new</span> HashSet&lt;&gt;());</span><br></pre></td></tr></table></figure>
<h4 id="1-无参构造函数"><a href="#1-无参构造函数" class="headerlink" title="1. 无参构造函数"></a>1. 无参构造函数</h4><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">public</span> <span class="title">LinkedList</span><span class="params">()</span> </span>&#123;&#125;</span><br></pre></td></tr></table></figure>
<p>无参构造函数没有任何操作，因为在其类的定义属性中以及包含了LinkedList初始化需要的一切，终端节点，节点个数。LinkedList类的重点在于节点的构成以及节点之间的操作。</p>
<h4 id="2-参数为集合类"><a href="#2-参数为集合类" class="headerlink" title="2. 参数为集合类"></a>2. 参数为集合类</h4><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/**</span></span><br><span class="line"><span class="comment">    * Constructs a list containing the elements of the specified</span></span><br><span class="line"><span class="comment">    * collection, in the order they are returned by the collection&#x27;s</span></span><br><span class="line"><span class="comment">    * iterator.</span></span><br><span class="line"><span class="comment">    *</span></span><br><span class="line"><span class="comment">    * <span class="doctag">@param</span>  c the collection whose elements are to be placed into this list</span></span><br><span class="line"><span class="comment">    * <span class="doctag">@throws</span> NullPointerException if the specified collection is null</span></span><br><span class="line"><span class="comment">    */</span></span><br><span class="line">   <span class="function"><span class="keyword">public</span> <span class="title">LinkedList</span><span class="params">(Collection&lt;? extends E&gt; c)</span> </span>&#123;</span><br><span class="line">       <span class="keyword">this</span>();</span><br><span class="line">       addAll(c);</span><br><span class="line">   &#125;</span><br></pre></td></tr></table></figure>
<p>通过遍历集合，加入LinkedList中</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">boolean</span> <span class="title">addAll</span><span class="params">(Collection&lt;? extends E&gt; c)</span> </span>&#123;</span><br><span class="line">    <span class="keyword">return</span> addAll(size, c);</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">boolean</span> <span class="title">addAll</span><span class="params">(<span class="keyword">int</span> index, Collection&lt;? extends E&gt; c)</span> </span>&#123;</span><br><span class="line">        checkPositionIndex(index);</span><br><span class="line"></span><br><span class="line">        Object[] a = c.toArray();</span><br><span class="line">        <span class="keyword">int</span> numNew = a.length;</span><br><span class="line">        <span class="keyword">if</span> (numNew == <span class="number">0</span>)</span><br><span class="line">            <span class="keyword">return</span> <span class="keyword">false</span>;</span><br><span class="line"></span><br><span class="line">        Node&lt;E&gt; pred, succ;</span><br><span class="line">        <span class="keyword">if</span> (index == size) &#123;</span><br><span class="line">            succ = <span class="keyword">null</span>;</span><br><span class="line">            pred = last;</span><br><span class="line">        &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">            succ = node(index);</span><br><span class="line">            pred = succ.prev;</span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">        <span class="keyword">for</span> (Object o : a) &#123;</span><br><span class="line">            <span class="meta">@SuppressWarnings(&quot;unchecked&quot;)</span> E e = (E) o;</span><br><span class="line">            Node&lt;E&gt; newNode = <span class="keyword">new</span> Node&lt;&gt;(pred, e, <span class="keyword">null</span>);</span><br><span class="line">            <span class="keyword">if</span> (pred == <span class="keyword">null</span>)</span><br><span class="line">                first = newNode;</span><br><span class="line">            <span class="keyword">else</span></span><br><span class="line">                pred.next = newNode;</span><br><span class="line">            pred = newNode;</span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">        <span class="keyword">if</span> (succ == <span class="keyword">null</span>) &#123;</span><br><span class="line">            last = pred;</span><br><span class="line">        &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">            pred.next = succ;</span><br><span class="line">            succ.prev = pred;</span><br><span class="line">        &#125;</span><br><span class="line"></span><br><span class="line">        size += numNew;</span><br><span class="line">        modCount++;</span><br><span class="line">        <span class="keyword">return</span> <span class="keyword">true</span>;</span><br><span class="line">    &#125;</span><br></pre></td></tr></table></figure>
<p>1.检查要插入的下标是否越界</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">private</span> <span class="keyword">void</span> <span class="title">checkPositionIndex</span><span class="params">(<span class="keyword">int</span> index)</span> </span>&#123;</span><br><span class="line">    <span class="keyword">if</span> (!isPositionIndex(index))</span><br><span class="line">        <span class="keyword">throw</span> <span class="keyword">new</span> IndexOutOfBoundsException(outOfBoundsMsg(index));</span><br><span class="line">&#125;</span><br><span class="line"></span><br><span class="line"><span class="function"><span class="keyword">private</span> <span class="keyword">boolean</span> <span class="title">isPositionIndex</span><span class="params">(<span class="keyword">int</span> index)</span> </span>&#123;</span><br><span class="line">	<span class="keyword">return</span> index &gt;= <span class="number">0</span> &amp;&amp; index &lt;= size;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
<p>2.取出集中中数据数组，并判断是否为空</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line">Object[] a = c.toArray();</span><br><span class="line"><span class="keyword">int</span> numNew = a.length;</span><br><span class="line"><span class="keyword">if</span> (numNew == <span class="number">0</span>)</span><br><span class="line">    <span class="keyword">return</span> <span class="keyword">false</span>;</span><br></pre></td></tr></table></figure>
<p>3.定义两个节点，用来保存要插入位置的前驱<code>pred</code>和后继<code>succ</code>。如果插入位置为尾部则将引用尾部节点，否则调用根据要插入的位置调用<code>node(int index)</code>来获取节点，后继引用将该节点，前驱引用该节点的上一个节点。</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><span class="line">Node&lt;E&gt; pred, succ;</span><br><span class="line"><span class="keyword">if</span> (index == size) &#123;</span><br><span class="line">    succ = <span class="keyword">null</span>;</span><br><span class="line">    pred = last;</span><br><span class="line">&#125; <span class="keyword">else</span> &#123;</span><br><span class="line">    succ = node(index);</span><br><span class="line">    pred = succ.prev;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line"><span class="function">Node&lt;E&gt; <span class="title">node</span><span class="params">(<span class="keyword">int</span> index)</span> </span>&#123;</span><br><span class="line">    <span class="comment">// assert isElementIndex(index);</span></span><br><span class="line"></span><br><span class="line">    <span class="keyword">if</span> (index &lt; (size &gt;&gt; <span class="number">1</span>)) &#123;</span><br><span class="line">        Node&lt;E&gt; x = first;</span><br><span class="line">        <span class="keyword">for</span> (<span class="keyword">int</span> i = <span class="number">0</span>; i &lt; index; i++)</span><br><span class="line">            x = x.next;</span><br><span class="line">        <span class="keyword">return</span> x;</span><br><span class="line">    &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">        Node&lt;E&gt; x = last;</span><br><span class="line">        <span class="keyword">for</span> (<span class="keyword">int</span> i = size - <span class="number">1</span>; i &gt; index; i--)</span><br><span class="line">            x = x.prev;</span><br><span class="line">        <span class="keyword">return</span> x;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
<p>在node()方法中，首先会对<code>传入的索引index与长度size/2进行比较</code>，如果index&gt;=size/2，那么说明节点在LinkedList的后半段，从后往前找会更加省时；如果index&lt;size/2，说明节点在LinkedList的前半段，从第一个节点顺序遍历，会更加容易找。</p>
<p>但如果这个数越靠近中间，那么get()方法遍历的时间也越长，效率也越低。而且随着LinkedList中的节点数量越来越大，get()的执行性能也会迅速下降。</p>
<p>4.变量集合，并构建<code>Node</code>节点。将节点前驱节点链接<code>pred</code>。并判断节点<code>pred</code>是否是空节点，如果为空，是头部，则将头部节点引用该节点，否则将节点<code>pred</code>的后继节点引用该节点。接着将<code>pred</code>节点引用该节点，继续下一个结点的创建。</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">for</span> (Object o : a) &#123;</span><br><span class="line">    <span class="meta">@SuppressWarnings(&quot;unchecked&quot;)</span> E e = (E) o;</span><br><span class="line">    Node&lt;E&gt; newNode = <span class="keyword">new</span> Node&lt;&gt;(pred, e, <span class="keyword">null</span>);</span><br><span class="line">    <span class="keyword">if</span> (pred == <span class="keyword">null</span>)</span><br><span class="line">        first = newNode;</span><br><span class="line">    <span class="keyword">else</span></span><br><span class="line">        pred.next = newNode;</span><br><span class="line">    pred = newNode;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
<p>5.判断后继节点<code>succ</code>是否为空，如果是，则说明插入位置为尾部，就将尾部节点<code>last</code>引用最后节点；否则，插入位置后面还有节点，将其链接起来。</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line"><span class="keyword">if</span> (succ == <span class="keyword">null</span>) &#123;</span><br><span class="line">    last = pred;</span><br><span class="line">&#125; <span class="keyword">else</span> &#123;</span><br><span class="line">    pred.next = succ;</span><br><span class="line">    succ.prev = pred;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
<p>6.最后将<code>size</code>修改</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br></pre></td><td class="code"><pre><span class="line">size += numNew;</span><br></pre></td></tr></table></figure>
<h3 id="三、添加元素"><a href="#三、添加元素" class="headerlink" title="三、添加元素"></a>三、添加元素</h3><p>添加元素的方法有很多</p>
<ul>
<li>添加到链表的头部：addFirst(E)</li>
<li>添加到链表的尾部：addLast(E)</li>
<li>顺序添加：add(E)</li>
<li>指定位置添加：add(int,E)</li>
<li>集合顺序添加到链表：addAll(Collection&lt;? extends E&gt;)</li>
<li>集合指定位置添加到链表：addAll(int,Collection&lt;? extends E&gt;)</li>
</ul>
<p>对于添加操作，是通过链表上节点的<code>prev</code>和<code>next</code>变量来进行节点之间的连接，分为三种情况</p>
<ul>
<li>插入头部</li>
</ul>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/**</span></span><br><span class="line"><span class="comment"> * Links e as first element.</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="function"><span class="keyword">private</span> <span class="keyword">void</span> <span class="title">linkFirst</span><span class="params">(E e)</span> </span>&#123;</span><br><span class="line">    <span class="keyword">final</span> Node&lt;E&gt; f = first;</span><br><span class="line">    <span class="keyword">final</span> Node&lt;E&gt; newNode = <span class="keyword">new</span> Node&lt;&gt;(<span class="keyword">null</span>, e, f);</span><br><span class="line">    first = newNode;</span><br><span class="line">    <span class="keyword">if</span> (f == <span class="keyword">null</span>)</span><br><span class="line">        last = newNode;</span><br><span class="line">    <span class="keyword">else</span></span><br><span class="line">        f.prev = newNode;</span><br><span class="line">    size++;</span><br><span class="line">    modCount++;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
<p><img src="link.jpg" alt="link"></p>
<ul>
<li>插入尾部</li>
</ul>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">/**</span></span><br><span class="line"><span class="comment"> * Links e as last element.</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="function"><span class="keyword">void</span> <span class="title">linkLast</span><span class="params">(E e)</span> </span>&#123;</span><br><span class="line">    <span class="keyword">final</span> Node&lt;E&gt; l = last;</span><br><span class="line">    <span class="keyword">final</span> Node&lt;E&gt; newNode = <span class="keyword">new</span> Node&lt;&gt;(l, e, <span class="keyword">null</span>);</span><br><span class="line">    last = newNode;</span><br><span class="line">    <span class="keyword">if</span> (l == <span class="keyword">null</span>)</span><br><span class="line">        first = newNode;</span><br><span class="line">    <span class="keyword">else</span></span><br><span class="line">        l.next = newNode;</span><br><span class="line">    size++;</span><br><span class="line">    modCount++;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
<p>与插入头部类似</p>
<ul>
<li>插入头尾中间区域</li>
</ul>
<p>首先要检查索引是否越界，调用<code>node()</code>方法查找节点，按位置插入，要判断是不是第一个结点，如果是，要将头部引用执行该节点。</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">private</span> <span class="keyword">boolean</span> <span class="title">isPositionIndex</span><span class="params">(<span class="keyword">int</span> index)</span> </span>&#123;</span><br><span class="line">        <span class="keyword">return</span> index &gt;= <span class="number">0</span> &amp;&amp; index &lt;= size;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line"><span class="function">Node&lt;E&gt; <span class="title">node</span><span class="params">(<span class="keyword">int</span> index)</span> </span>&#123;</span><br><span class="line">        <span class="comment">// assert isElementIndex(index);</span></span><br><span class="line"></span><br><span class="line">        <span class="keyword">if</span> (index &lt; (size &gt;&gt; <span class="number">1</span>)) &#123;</span><br><span class="line">            Node&lt;E&gt; x = first;</span><br><span class="line">            <span class="keyword">for</span> (<span class="keyword">int</span> i = <span class="number">0</span>; i &lt; index; i++)</span><br><span class="line">                x = x.next;</span><br><span class="line">            <span class="keyword">return</span> x;</span><br><span class="line">        &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">            Node&lt;E&gt; x = last;</span><br><span class="line">            <span class="keyword">for</span> (<span class="keyword">int</span> i = size - <span class="number">1</span>; i &gt; index; i--)</span><br><span class="line">                x = x.prev;</span><br><span class="line">            <span class="keyword">return</span> x;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line"><span class="comment">/**</span></span><br><span class="line"><span class="comment"> * Inserts element e before non-null Node succ.</span></span><br><span class="line"><span class="comment"> */</span></span><br><span class="line"><span class="function"><span class="keyword">void</span> <span class="title">linkBefore</span><span class="params">(E e, Node&lt;E&gt; succ)</span> </span>&#123;</span><br><span class="line">    <span class="comment">// assert succ != null;</span></span><br><span class="line">    <span class="keyword">final</span> Node&lt;E&gt; pred = succ.prev;</span><br><span class="line">    <span class="keyword">final</span> Node&lt;E&gt; newNode = <span class="keyword">new</span> Node&lt;&gt;(pred, e, succ);</span><br><span class="line">    succ.prev = newNode;</span><br><span class="line">    <span class="keyword">if</span> (pred == <span class="keyword">null</span>)</span><br><span class="line">        first = newNode;</span><br><span class="line">    <span class="keyword">else</span></span><br><span class="line">        pred.next = newNode;</span><br><span class="line">    size++;</span><br><span class="line">    modCount++;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
<h3 id="四、获取元素"><a href="#四、获取元素" class="headerlink" title="四、获取元素"></a>四、获取元素</h3><ul>
<li>按照索引获取元素：get(int)</li>
<li>获取第一个元素：getFirst()</li>
<li>获取第二个元素：getLas()</li>
</ul>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">public</span> E <span class="title">get</span><span class="params">(<span class="keyword">int</span> index)</span> </span>&#123;</span><br><span class="line">    checkElementIndex(index);</span><br><span class="line">    <span class="keyword">return</span> node(index).item;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
<p>首先检查索引是否越界，调用<code>node(index)</code>方法</p>
<h3 id="五、修改元素"><a href="#五、修改元素" class="headerlink" title="五、修改元素"></a>五、修改元素</h3><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">public</span> E <span class="title">set</span><span class="params">(<span class="keyword">int</span> index, E element)</span> </span>&#123;</span><br><span class="line">    checkElementIndex(index);</span><br><span class="line">    Node&lt;E&gt; x = node(index);</span><br><span class="line">    E oldVal = x.item;</span><br><span class="line">    x.item = element;</span><br><span class="line">    <span class="keyword">return</span> oldVal;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
<h3 id="六、删除元素"><a href="#六、删除元素" class="headerlink" title="六、删除元素"></a>六、删除元素</h3><p>删除元素的方法有：</p>
<ul>
<li><p>默认删除第一个元素：remove()</p>
</li>
<li><p>依据元素删除：remove(Object o)</p>
</li>
<li>依据索引删除：remove(int index)</li>
<li>移除第一个节点：removeFirst()</li>
<li>移除最后一个节点：removeLast()</li>
</ul>
<p>对于删除元素也是在<code>prev</code>和<code>next</code>变量中来调节点与点之间的关系.</p>
<h4 id="1-依据元素删除"><a href="#1-依据元素删除" class="headerlink" title="1. 依据元素删除"></a>1. 依据元素删除</h4><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">public</span> <span class="keyword">boolean</span> <span class="title">remove</span><span class="params">(Object o)</span> </span>&#123;</span><br><span class="line">    <span class="keyword">if</span> (o == <span class="keyword">null</span>) &#123;</span><br><span class="line">        <span class="keyword">for</span> (Node&lt;E&gt; x = first; x != <span class="keyword">null</span>; x = x.next) &#123;</span><br><span class="line">            <span class="keyword">if</span> (x.item == <span class="keyword">null</span>) &#123;</span><br><span class="line">                unlink(x);</span><br><span class="line">                <span class="keyword">return</span> <span class="keyword">true</span>;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">        <span class="keyword">for</span> (Node&lt;E&gt; x = first; x != <span class="keyword">null</span>; x = x.next) &#123;</span><br><span class="line">            <span class="keyword">if</span> (o.equals(x.item)) &#123;</span><br><span class="line">                unlink(x);</span><br><span class="line">                <span class="keyword">return</span> <span class="keyword">true</span>;</span><br><span class="line">            &#125;</span><br><span class="line">        &#125;</span><br><span class="line">    &#125;</span><br><span class="line">    <span class="keyword">return</span> <span class="keyword">false</span>;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
<p>从源码中看出，LinkedList可以添加值为null的节点，需要将所有节点遍历一遍查找该值，并调用<code>unlink()</code>方法移除节点。</p>
<figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br></pre></td><td class="code"><pre><span class="line"><span class="function">E <span class="title">unlink</span><span class="params">(Node&lt;E&gt; x)</span> </span>&#123;</span><br><span class="line">    <span class="comment">// assert x != null;</span></span><br><span class="line">    <span class="keyword">final</span> E element = x.item;</span><br><span class="line">    <span class="keyword">final</span> Node&lt;E&gt; next = x.next;</span><br><span class="line">    <span class="keyword">final</span> Node&lt;E&gt; prev = x.prev;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">if</span> (prev == <span class="keyword">null</span>) &#123;</span><br><span class="line">        first = next;</span><br><span class="line">    &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">        prev.next = next;</span><br><span class="line">        x.prev = <span class="keyword">null</span>;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    <span class="keyword">if</span> (next == <span class="keyword">null</span>) &#123;</span><br><span class="line">        last = prev;</span><br><span class="line">    &#125; <span class="keyword">else</span> &#123;</span><br><span class="line">        next.prev = prev;</span><br><span class="line">        x.next = <span class="keyword">null</span>;</span><br><span class="line">    &#125;</span><br><span class="line"></span><br><span class="line">    x.item = <span class="keyword">null</span>;</span><br><span class="line">    size--;</span><br><span class="line">    modCount++;</span><br><span class="line">    <span class="keyword">return</span> element;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
<p>在unlink()方法中，<code>将要移除的节点的前节点的后继引用指向移除节点的后节点，移除节点的后节点的前驱引用指向移除节点的前节点</code>,并将移除的节点的数据、前后驱引用设置为空</p>
<h4 id="2-依据元素删除"><a href="#2-依据元素删除" class="headerlink" title="2. 依据元素删除"></a>2. 依据元素删除</h4><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">public</span> E <span class="title">remove</span><span class="params">(<span class="keyword">int</span> index)</span> </span>&#123;</span><br><span class="line">    checkElementIndex(index);</span><br><span class="line">    <span class="keyword">return</span> unlink(node(index));</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
<p>检查索引，根据索引查找节点，调用unlink()方法移除节点</p>
<h3 id="3-默认删除"><a href="#3-默认删除" class="headerlink" title="3. 默认删除"></a>3. 默认删除</h3><figure class="highlight java"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br></pre></td><td class="code"><pre><span class="line"><span class="function"><span class="keyword">public</span> E <span class="title">remove</span><span class="params">()</span> </span>&#123;</span><br><span class="line">    <span class="keyword">return</span> removeFirst();</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>
<h3 id="七、实现了Deque接口-双端队列"><a href="#七、实现了Deque接口-双端队列" class="headerlink" title="七、实现了Deque接口,双端队列"></a>七、实现了<code>Deque</code>接口,双端队列</h3><h4 id="1-队列"><a href="#1-队列" class="headerlink" title="1.队列"></a>1.队列</h4><ul>
<li>poll()、pollFirst()、pollLast()      删除并返回值</li>
<li>peek()、peekFirst()、peekLast()  返回值</li>
</ul>
<h4 id="2-栈"><a href="#2-栈" class="headerlink" title="2. 栈"></a>2. 栈</h4><ul>
<li>push(E)、pop()</li>
</ul>


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          <ol class="toc-nav"><li class="toc-nav-item toc-nav-level-3"><a class="toc-nav-link" href="#%E4%B8%80%E3%80%81%E5%B1%9E%E6%80%A7"><span class="toc-nav-number">1.</span> <span class="toc-nav-text">一、属性</span></a></li><li class="toc-nav-item toc-nav-level-3"><a class="toc-nav-link" href="#%E4%BA%8C%E3%80%81%E6%9E%84%E9%80%A0%E5%87%BD%E6%95%B0"><span class="toc-nav-number">2.</span> <span class="toc-nav-text">二、构造函数</span></a><ol class="toc-nav-child"><li class="toc-nav-item toc-nav-level-4"><a class="toc-nav-link" href="#1-%E6%97%A0%E5%8F%82%E6%9E%84%E9%80%A0%E5%87%BD%E6%95%B0"><span class="toc-nav-number">2.1.</span> <span class="toc-nav-text">1. 无参构造函数</span></a></li><li class="toc-nav-item toc-nav-level-4"><a class="toc-nav-link" href="#2-%E5%8F%82%E6%95%B0%E4%B8%BA%E9%9B%86%E5%90%88%E7%B1%BB"><span class="toc-nav-number">2.2.</span> <span class="toc-nav-text">2. 参数为集合类</span></a></li></ol></li><li class="toc-nav-item toc-nav-level-3"><a class="toc-nav-link" href="#%E4%B8%89%E3%80%81%E6%B7%BB%E5%8A%A0%E5%85%83%E7%B4%A0"><span class="toc-nav-number">3.</span> <span class="toc-nav-text">三、添加元素</span></a></li><li class="toc-nav-item toc-nav-level-3"><a class="toc-nav-link" href="#%E5%9B%9B%E3%80%81%E8%8E%B7%E5%8F%96%E5%85%83%E7%B4%A0"><span class="toc-nav-number">4.</span> <span class="toc-nav-text">四、获取元素</span></a></li><li class="toc-nav-item toc-nav-level-3"><a class="toc-nav-link" href="#%E4%BA%94%E3%80%81%E4%BF%AE%E6%94%B9%E5%85%83%E7%B4%A0"><span class="toc-nav-number">5.</span> <span class="toc-nav-text">五、修改元素</span></a></li><li class="toc-nav-item toc-nav-level-3"><a class="toc-nav-link" href="#%E5%85%AD%E3%80%81%E5%88%A0%E9%99%A4%E5%85%83%E7%B4%A0"><span class="toc-nav-number">6.</span> <span class="toc-nav-text">六、删除元素</span></a><ol class="toc-nav-child"><li class="toc-nav-item toc-nav-level-4"><a class="toc-nav-link" href="#1-%E4%BE%9D%E6%8D%AE%E5%85%83%E7%B4%A0%E5%88%A0%E9%99%A4"><span class="toc-nav-number">6.1.</span> <span class="toc-nav-text">1. 依据元素删除</span></a></li><li class="toc-nav-item toc-nav-level-4"><a class="toc-nav-link" href="#2-%E4%BE%9D%E6%8D%AE%E5%85%83%E7%B4%A0%E5%88%A0%E9%99%A4"><span class="toc-nav-number">6.2.</span> <span class="toc-nav-text">2. 依据元素删除</span></a></li></ol></li><li class="toc-nav-item toc-nav-level-3"><a class="toc-nav-link" href="#3-%E9%BB%98%E8%AE%A4%E5%88%A0%E9%99%A4"><span class="toc-nav-number">7.</span> <span class="toc-nav-text">3. 默认删除</span></a></li><li class="toc-nav-item toc-nav-level-3"><a class="toc-nav-link" href="#%E4%B8%83%E3%80%81%E5%AE%9E%E7%8E%B0%E4%BA%86Deque%E6%8E%A5%E5%8F%A3-%E5%8F%8C%E7%AB%AF%E9%98%9F%E5%88%97"><span class="toc-nav-number">8.</span> <span class="toc-nav-text">七、实现了Deque接口,双端队列</span></a><ol class="toc-nav-child"><li class="toc-nav-item toc-nav-level-4"><a class="toc-nav-link" href="#1-%E9%98%9F%E5%88%97"><span class="toc-nav-number">8.1.</span> <span class="toc-nav-text">1.队列</span></a></li><li class="toc-nav-item toc-nav-level-4"><a class="toc-nav-link" href="#2-%E6%A0%88"><span class="toc-nav-number">8.2.</span> <span class="toc-nav-text">2. 栈</span></a></li></ol></li></ol>
        
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    }
    // get search zip version
    $.get('/searchVersion.json?t=' + (+new Date()), function (res) {
      if (localStorage.getItem('searchVersion') !== res) {
        localStorage.setItem('searchVersion', res);
        initSearchJson();
      }
    });

    function initSearchJson() {
      initLoad(['/search.flv'], {
        loadOptions: {
          success: function (obj) {
            localStorage.setItem('searchJson', obj['search.json'])
          },
          error: function (e) {
            return console.log(e)
          }
        },
        returnOptions: {
          'json': TYPE_TEXT
        },
        mimeOptions: {
          'json': 'application/json'
        }
      })
    }
    // search function;
    var searchFunc = function (search_id, content_id) {
      'use strict';
      isfetched = true;
      var datas = JSON.parse(localStorage.getItem('searchJson'));
      // console.log(search_id)
      var input = document.getElementById(search_id);
      var resultContent = document.getElementById(content_id);
      var inputEventFunction = function () {
        var searchText = input.value.trim().toLowerCase();
        var keywords = searchText.split(/[\s\-]+/);
        if (keywords.length > 1) {
          keywords.push(searchText);
        }
        var resultItems = [];
        if (searchText.length > 0) {
          // perform local searching
          datas.forEach(function (data) {
            var isMatch = false;
            var hitCount = 0;
            var searchTextCount = 0;
            var title = data.title
              ? data.title.trim()
              : '';
            var titleInLowerCase = title.toLowerCase();
            var content = data.content
              ? data.content.trim().replace(/<[^>]+>/g, "")
              : '';
            var contentInLowerCase = content.toLowerCase();
            var articleUrl = decodeURIComponent(data.url);

            var date = data.date;
            var dateTime = date.replace(/T/, " ").replace(/.000Z/, "");
            var imgUrl = data.header_img;
            


            var indexOfTitle = [];
            var indexOfContent = [];
            // only match articles with not empty titles
            keywords.forEach(function (keyword) {
              function getIndexByWord(word, text, caseSensitive) {
                var wordLen = word.length;
                if (wordLen === 0) {
                  return [];
                }
                var startPosition = 0,
                  position = [],
                  index = [];
                if (!caseSensitive) {
                  text = text.toLowerCase();
                  word = word.toLowerCase();
                }
                while ((position = text.indexOf(word, startPosition)) > -1) {
                  index.push({position: position, word: word});
                  startPosition = position + wordLen;
                }
                return index;
              }
              indexOfTitle = indexOfTitle.concat(getIndexByWord(keyword, titleInLowerCase, false));
              indexOfContent = indexOfContent.concat(getIndexByWord(keyword, contentInLowerCase, false));
            });
            if (indexOfTitle.length > 0 || indexOfContent.length > 0) {
              isMatch = true;
              hitCount = indexOfTitle.length + indexOfContent.length;
            }
            // show search results
            if (isMatch) {
              // sort index by position of keyword
              [indexOfTitle, indexOfContent].forEach(function (index) {
                index.sort(function (itemLeft, itemRight) {
                  if (itemRight.position !== itemLeft.position) {
                    return itemRight.position - itemLeft.position;
                  } else {
                    return itemLeft.word.length - itemRight.word.length;
                  }
                });
              });
              // merge hits into slices
              function mergeIntoSlice(text, start, end, index) {
                var item = index[index.length - 1];
                var position = item.position;
                var word = item.word;
                var hits = [];
                var searchTextCountInSlice = 0;
                while (position + word.length <= end && index.length != 0) {
                  if (word === searchText) {
                    searchTextCountInSlice++;
                  }
                  hits.push({position: position, length: word.length});
                  var wordEnd = position + word.length;
                  // move to next position of hit
                  index.pop();
                  while (index.length != 0) {
                    item = index[index.length - 1];
                    position = item.position;
                    word = item.word;
                    if (wordEnd > position) {
                      index.pop();
                    } else {
                      break;
                    }
                  }
                }
                searchTextCount += searchTextCountInSlice;
                return {hits: hits, start: start, end: end, searchTextCount: searchTextCountInSlice};
              }
              var slicesOfTitle = [];
              if (indexOfTitle.length != 0) {
                slicesOfTitle.push(mergeIntoSlice(title, 0, title.length, indexOfTitle));
              }
              var slicesOfContent = [];
              while (indexOfContent.length != 0) {
                var item = indexOfContent[indexOfContent.length - 1];
                var position = item.position;
                var word = item.word;
                // cut out 100 characters
                var start = position - 20;
                var end = position + 80;
                if (start < 0) {
                  start = 0;
                }
                if (end < position + word.length) {
                  end = position + word.length;
                }
                if (end > content.length) {
                  end = content.length;
                }
                slicesOfContent.push(mergeIntoSlice(content, start, end, indexOfContent));
              }
              // sort slices in content by search text's count and hits' count
              slicesOfContent.sort(function (sliceLeft, sliceRight) {
                if (sliceLeft.searchTextCount !== sliceRight.searchTextCount) {
                  return sliceRight.searchTextCount - sliceLeft.searchTextCount;
                } else if (sliceLeft.hits.length !== sliceRight.hits.length) {
                  return sliceRight.hits.length - sliceLeft.hits.length;
                } else {
                  return sliceLeft.start - sliceRight.start;
                }
              });
              // select top N slices in content
              var upperBound = parseInt('1');
              if (upperBound >= 0) {
                slicesOfContent = slicesOfContent.slice(0, upperBound);
              }
              // highlight title and content
              function highlightKeyword(text, slice) {
                var result = '';
                var prevEnd = slice.start;
                slice.hits.forEach(function (hit) {
                  result += text.substring(prevEnd, hit.position);
                  var end = hit.position + hit.length;
                  result += '<b class="search-keyword">' + text.substring(hit.position, end) + '</b>';
                  prevEnd = end;
                });
                result += text.substring(prevEnd, slice.end);
                return result;
              }
              var resultItem = '';

              // if (slicesOfTitle.length != 0) {   resultItem += "<li><a target='_blank' href='" + articleUrl + "' class='search-result-title'>" + highlightKeyword(title, slicesOfTitle[0]) + "</a>"; } else {   resultItem += "<li><a target='_blank' href='" +
              // articleUrl + "' class='search-result-title'>" + title + "</a>"; } slicesOfContent.forEach(function (slice) {   resultItem += "<a target='_blank' href='" + articleUrl + "'><p class=\"search-result\">" + highlightKeyword(content, slice) +
              // "...</p></a>"; }); resultItem += "</li>";

              if (slicesOfTitle.length != 0) {
                resultItem += "<a target='_blank' href='" + articleUrl + "' class='search-result'><div class='search-result-left'><div class='search-result-title'>" + highlightKeyword(title, slicesOfTitle[0]) + "</div><time class='search-result-date'>" + dateTime + "</time>";
              } else {
                resultItem += "<a target='_blank' href='" + articleUrl + "' class='search-result'><div class='search-result-left'><div class='search-result-title'>" + title + "</div><time class='search-result-date'>" + dateTime + "</time>";
              }
              slicesOfContent.forEach(function (slice) {
                resultItem += "<p class=\"search-result-content\">" + highlightKeyword(content, slice) + "...</p>";
              });
              resultItem += "</div><div class='search-result-right'><img class='media-image' src='" + imgUrl + "' width='64px' height='48px'></img></div></a>";

              resultItems.push({item: resultItem, searchTextCount: searchTextCount, hitCount: hitCount, id: resultItems.length});
            }
          })
        };

        if (keywords.length === 1 && keywords[0] === "") {
          resultContent.innerHTML = '<div id="no-result"></div>'
        } else if (resultItems.length === 0) {
          resultContent.innerHTML = '<div id="no-result"></div>'
        } else {
          resultItems.sort(function (resultLeft, resultRight) {
            if (resultLeft.searchTextCount !== resultRight.searchTextCount) {
              return resultRight.searchTextCount - resultLeft.searchTextCount;
            } else if (resultLeft.hitCount !== resultRight.hitCount) {
              return resultRight.hitCount - resultLeft.hitCount;
            } else {
              return resultRight.id - resultLeft.id;
            }
          });
          var searchResultList = '<div class=\"search-result-list\">';
          resultItems.forEach(function (result) {
            searchResultList += result.item;
          })
          searchResultList += "</div>";
          resultContent.innerHTML = searchResultList;
        }
      }
      if ('auto' === 'auto') {
        input.addEventListener('input', inputEventFunction);
      } else {
        $('.search-icon').click(inputEventFunction);
        input.addEventListener('keypress', function (event) {
          if (event.keyCode === 13) {
            inputEventFunction();
          }
        });
      }
      // remove loading animation
      $('body').css('overflow', '');
      proceedsearch();
    }
    // handle and trigger popup window;
    $('.popup-trigger').click(function (e) {
      e.stopPropagation();
      if (isfetched === false) {
        searchFunc('local-search-input', 'local-search-result');
      } else {
        proceedsearch();
      };
    });
    $('.popup-btn-close').click(onPopupClose);
    $('.popup').click(function (e) {
      e.stopPropagation();
    });
    $(document).on('keyup', function (event) {
      var shouldDismissSearchPopup = event.which === 27 && $('.search-popup').is(':visible');
      if (shouldDismissSearchPopup) {
        onPopupClose();
      }
    });

    document.addEventListener('mouseup', (e) => {
      var _con = document.querySelector(".local-search-content");
      if (_con) {
        if (!_con.contains(e.target)) {
          onPopupClose();
        }
      }
    });
  </script>


		
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    MathJax.Hub.Queue(function() {
        var all = MathJax.Hub.getAllJax();
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